2004 GMC Sierra Buildup - GM Performance Parts LSX376 Engine

2004 GMC Sierra Buildup Factory Engine And Transmission

When it came time to pull the worn-out, 150,000+ miles 4.8L V-8 out of the '04 GMC Sierra we nicknamed Project Novakane, we didn't want a little more power, we wanted monster power. Thankfully, making big power out of a relatively small engine is as easy as intelligently choosing the right combination of engine, power adder, drivetrain, and also understanding the limits to which you can push your combo. This part of the buildup was the most intense, most heavily researched, and most exciting, after all, the engine is the heart and soul of a performance truck.

Before we could dream of burnouts and high-speed conquests, we first needed to remove the tired original 4.8L. To do this, we drove the Sierra into our Source Interlink Tech Center and got to work removing the necessary parts. Working on a '99+ GM truck is quite easy and pulling the engine, with the right tools and some help, isn't a difficult job. We started by removing the hood, then drained the coolant, and began the job of removing the serpentine belt, alternator, throttle body, and intake manifold. Each bolt that was removed was placed in a Ziploc bag and cataloged for easy reference when the new engine is installed. On the GM trucks, a cool trick is simply unbolting the A/C compressor and bracket, along with the power steering pump and bracket, and swinging them aside without disconnecting the hoses, which would require a costly flush and refill. With each sensor disconnected and wire labeled for reference, we removed the driveshaft, disconnected the manual transmission shifter, and unbolted the transmission and engine mounts, along with the front crossmember, and then bolted the engine leveler to the block. A couple of tugs with the engine hoist later, our 4.8L was out of the truck and our Sierra was ready for some real power!

2004 GMC Sierra Buildup Factory LS Engine

We squeezed so much power out of our 150,000+ mile factory 4.8L, it finally gave up the fight. Rather than go through it and rebuild it, we opted to peruse the GM Performance Parts catalog and place an order. Before we could swap in the new combo, we first needed to pull the original LS-based small-block.

We squeezed so much power out of our 150,000+ mile factory 4.8L, it finally gave up the fi

Looking around the performance car world, one particular supercar stood out time and time again-the LS9-equipped Corvette ZR1. Combining a supercharger with the tried and true (albeit modified and reinforced) LS3 under the hood, the new engine helps the ZR1 outperform other cars costing twice as much. Backing the blown small-block is a heavy-duty Tremec six-speed that helps propel the 'Vette to incredible performance numbers. Knowing that the GM Performance engineers are some of the best in the world, we're going to use the ZR1 as inspiration for Project Novakane. Hunting around for an appropriate long-block, we came across GM Performance Parts newest member of the LSX family, the LSX376. We officially had our first "lightbulb" moment and knew this engine was going to power our 4,300-pound truck into warp speed for the long haul.

Starting with an economical LSX Bow Tie block, the GM Performance Parts engineers added high-flow LS3-style L92 heads and 9:1 low-compression forged-aluminum pistons for a boost-friendly, high-revving engine that packs a wallop in a 376ci small-block package. Using the stock LS3 fuel-injection manifold and throttle-body, the LSX376 creates 450 hp at 5,900 rpm and 444 lb-ft of torque at 4,600 rpm, however, with the low-compression pistons, boost is what this engine lives for. Designed for 6-8 psi of boost, the LSX376 can safely live around the 620 hp range and still deliver nearly 20 mpg on the highway. If boost is what the LSX376 wants, then boost is what we'll give it.

It's not necessary to remove the hood, but it does make life a whole lot easier, so we went ahead and took it off. To make realigning it a breeze, we unbolted the two hinge bolts, not the hood bolts.
It's not necessary to remove the hood, but it does make life a whole lot easier, so we wen
It may look ridiculous, but our $10 kiddie pool worked perfectly for draining the coolant. With the late-model GM trucks not having a traditional radiator petcock, draining the fluid by pulling the radiator hoses can be extremely messy. Best $10 we spent in a long time.
It may look ridiculous, but our $10 kiddie pool worked perfectly for draining the coolant.
Once the battery was disconnected, and the air intake tube and serpentine belts removed, we could remove the A/C compressor and power steering pump. Rather than opening up either system, we simply unbolted each bracket and swung the units to the side.
Once the battery was disconnected, and the air intake tube and serpentine belts removed, w

An absolutely must for a big job like this, each bolt was bagged and labeled for a complete catalog of what we had and where it belonged. Each sensor and wire was also labeled for easy identification.
An absolutely must for a big job like this, each bolt was bagged and labeled for a complet
With each sensor unplugged, the coil packs removed, intake manifold pulled free, and the exhaust unbolted, we moved to the transmission. We pulled the engine and tranny as one unit, but we still needed to remove the transmission shifter. A 15/16-inch wrench was used to remove the stick and a T-10 Torx bit was used to removed the shifter boot bolts.
With each sensor unplugged, the coil packs removed, intake manifold pulled free, and the e
Back underneath the truck, the driveshaft was pulled free and the transmission mount bolt removed. It should also be noted that a rag was used to collect the oil draining out of the output shaft. The driveshaft was then removed and all of the tranny sensors were disconnected.
Back underneath the truck, the driveshaft was pulled free and the transmission mount bolt

Using four bolts from the A/C compressor and power steering brackets as mounting points, the engine leveler was connected to the engine hoist. The leveler was very important, as it allowed us to alter the position of the engine/tranny while getting it out of the engine bay.
Using four bolts from the A/C compressor and power steering brackets as mounting points, t
As our models show us where the gun show is, the engine and tranny were pulled free. As you can see, the motor mounts have been removed for added wiggle room and the front crossmember was unbolted for oil pan clearance.
As our models show us where the gun show is, the engine and tranny were pulled free. As yo
Using the Corvette's 638hp LS9 engine as inspiration, we wanted to build a comparable LS engine of our own. All we had to do was figure out the right combination of parts to make our Novakane project scream.
Using the Corvette's 638hp LS9 engine as inspiration, we wanted to build a comparable LS e

Now for the fun stuff. GM Performance Part's LSX engines are well known throughout the racing community as an economical and darn-near bulletproof foundation. These iron blocks can support up to 2,000 hp. We'd be happy with 750.
Now for the fun stuff. GM Performance Part's LSX engines are well known throughout the rac
Our horsepower search ended when we came across GMPP's newest member of the LSX family, the LSX376.
Our horsepower search ended when we came across GMPP's newest member of the LSX family, th
Using the LSX Bow Tie block, the GMPP team stuffed it with 9:1 forged-aluminum pistons and then bolted on high-flow LS3-style L92 heads for a rev-happy engine that is begging for boost.
Using the LSX Bow Tie block, the GMPP team stuffed it with 9:1 forged-aluminum pistons and